There is a need for a minimally obtrusive nasal interface, patient circuit tubing and ventilation system that delivers mechanical ventilatory support or positive airway pressure, while minimizing exhalation resistance and permitting less encumbered movement and/or ambulation of a patient so as to facilitate mobility of the patient and/or to allow activities of daily living. There are a range of clinical syndromes that require ventilation therapy that would benefit from such an interface and system, such as respiratory insufficiency, chronic obstructive lung or pulmonary disease (most commonly referred to as COPD), interstitial lung disease, fibrosis, acute respiratory distress syndrome (ARDS), airway or sleep disordered breathing, congestive heart failure and neuromuscular impairment.
There are two general types of mechanical ventilation (MV) modes. A first type delivers gas to a patient based on a frequency selected by the clinician which is independent of patient activity. This type of ventilation, known as controlled mechanical ventilation, is used when the ventilator is needed to breathe for the patient such as when the patient is non-alert, sedated, unresponsive or paralyzed. A second type of ventilation, known as assisted mechanical ventilation, or assisted ventilation, or augmented ventilation, delivers gas to the patient in response to an inspiratory effort generated by the patient. This type of ventilation helps the patient breathe, such as when the patient has respiratory insufficiency and/or dyspnea associated with COPD. There are also ventilators and modes of ventilation that combine the two modes of ventilation described above.
Certain invasive MV therapies connect to the patient by intubating the patient with a endotracheal tube, which is a tube inserted in the patient's mouth that extends to their voice box, or with a cuffed or uncuffed tracheal tube, which is a tube inserted through a stoma in the patient's throat area. While helpful in supporting the work of breathing, the patient interfaces used for invasive MV are obtrusive and/or invasive to the user, and obviously would not facilitate mobility or activities of daily living of the patient. Non-invasive mechanical ventilation (NIV) therapies also are known that ventilate a patient with a face or nasal mask rather than requiring intubation or tracheal tube. However, known non-invasive face or nasal masks are bulky and cumbersome and require a patient circuit with large diameter tubing that restricts movement and is also bulky and cumbersome. The non-invasive nasal masks used in these forms of mechanical ventilation operate using a closed gas circuit. A closed circuit system requires the mask to create a gas/air seal against the nose and/or mouth which can be uncomfortable to the patient. The bulky nature of known masks and patient circuits create a ‘dead space’ in the hollow areas of the mask and patient circuit. This dead space, coupled with the requirement of a closed system result in carbon dioxide (CO2) accumulating in the ‘dead space’ or hollow areas of the mask and patient circuit. The accumulation of CO2 needs to be flushed out of the patient circuit or mask to avoid the problem of the patient re-breathing CO2. The CO2 is flushed out the dead space by maintaining a constant low pressure in the ventilator, mask and patient circuit system. This constant low pressure creates exhalation resistance that is sometimes uncomfortable to the patient. Also, closed circuit ventilation systems increase the risk of the ventilator over pressurizing the patient's lungs, which can result in trauma to the airway tissues and then longer-term patient ventilator dependency. Consequently, known invasive and non-invasive mechanical ventilation systems do not facilitate activities of daily living of the patient or mobility and present risks of trauma to the patient's breathing tissues.
For treating sleep disorders such as sleep disordered breathing (SDB), the preferred ventilation therapies are continuous positive airway pressure (CPAP) and bi-level positive airway pressure (BiPAP). CPAP and BiPAP are a variant of mechanical non-invasive ventilation. Positive pressure applied by the ventilator in the form of CPAP or BiPAP is connected to the patient by a nasal or face mask that seals against the nose or face. The seal allows CPAP and BiPAP to operate as a closed circuit ventilation system and to treat sleep disordered breathing by pressurizing the upper airways and thereby preventing upper airway obstruction. While effective, this therapy has poor patient compliance because the patient interface and corresponding patient circuit tubing is obtrusive to the patient. As with mechanical invasive and non-invasive ventilation, the bulky nature of the CPAP and BiPAP masks and patient circuits create a ‘dead space’ in the hollow areas of the mask and patient circuit. This dead space, coupled with the requirement of a closed system result in CO2 accumulating in the ‘dead space’ or hollow areas of the mask and patient circuit. The accumulation of CO2 needs to be flushed out of the patient circuit or mask to avoid the problem of the patient re-breathing CO2. The CO2 is flushed out of the dead space by maintaining a constant low pressure in the ventilator, mask and patient circuit system. This constant low pressure creates exhalation resistance that is sometimes uncomfortable to the patient. Also, the closed circuit ventilation systems, such as CPAP and BiPAP, require the patient, in most instances, to unnaturally breathe through both a mask and gas delivery circuit, which can be uncomfortable.
Oxygen therapies are categorically different and distinct from mechanical ventilation therapies. Oxygen therapy increases the concentration of oxygen in the patient's lungs and other organs, which can increase lifespan of patients suffering from the above noted syndromes. While oxygen therapy has been demonstrated to improve lifespan, there is a lack of evidence demonstrating that oxygen therapy can reduce the severe feelings of breathlessness, work of breathing and discomfort a patient experiences resulting from the above noted syndromes. Consequently, oxygen therapies, e.g., continuous flow and pulsed flow, are used for far less severe forms of the noted syndromes than mechanical ventilation therapies. Oxygen therapies work by utilizing nasal cannulas or masks to deliver concentrated oxygen to the patient. Concentrated oxygen is delivered to the patient in a ‘continuous’ flow rate that is provided during the patient's inspiratory and expiratory breathing cycles, using a set continuous liter per minute (LPM) flow of oxygen. Also, concentrated oxygen is delivered to the patient in an ‘intermittent’ flow rate using oxygen therapy devices known as oxygen conservers. Oxygen conserver devices deliver an intermittent flow of oxygen only during the patient's inspiratory breathing cycle. Mechanical ventilation therapy, on the other hand, has decades of well-established evidence demonstrating a significant reduction in breathlessness, work of breathing, and discomfort experienced by patients that suffer from the above noted syndromes. Mechanical ventilation therapies can both utilize concentrated oxygen to improve lifespan and provide mechanical breathing support to improve breathing function, i.e., reduce breathlessness, work of breathing and patient discomfort. Correspondingly, mechanical ventilation therapy is different than oxygen therapy and therefore is used to treat patient populations with more severe forms of the above noted syndromes.
One or more of the above-identified disadvantages of known therapies has been attempted to be solved by a non-invasive open ventilation (NIOV) system recently developed by Breathe Technologies, Inc. of Irvine, Calif. that is used with bottled oxygen to deliver augmented O2 tidal volume and entrained air during a patient's spontaneous breathing so as to deliver both ventilation and supplemental oxygen with every breath. This volume augmentation is provided via a nasal pillow interface having entrainment ports that are open to ambient air. Generally the system senses the patient's spontaneous breath through a sense port in the nasal interface, and then delivers the selected pressurized volume of oxygen. As oxygen is delivered, ambient air is entrained through the entrainment ports, and positive pressure is developed within the interface to supplement the patient's spontaneous breathing. Although the NIOV system facilitates mobility and activities of daily living, the nasal pillow interface circumferentially extends from below the patient's nose to partially circumscribe the patient's face on either side thereof in order to have a length that can accommodate a throat area of the interface, which is necessary to develop positive pressure within the interface prior to delivery of the air oxygen mixture to the patient. This throat area that circumscribes the patient's face also creates a ‘dead space’ in the hollow areas of the nasal pillow interface. In addition, the nasal interface requires a patient circuit with tubing that accommodates a first lumen for sensing the patient's breathing effort and a second lumen for delivering a pressurized volume of oxygen to the patient. Consequently, a diameter of tubing used with the nasal interface and patient circuit must have an overall larger outer diameter to accommodate the requirement of distinct sensing and delivery lumens. Thus when worn by the patient, the overall size and weight of the nasal interface and patient circuit tubing associated therewith is not insubstantial and may even be considered by some patients as cumbersome and/or burdensome.
Accordingly, there still exists a need in the art for minimally obtrusive nasal interfaces and patient circuits that deliver mechanical ventilatory support or positive airway pressure, while permitting less encumbered movement so as to facilitate mobility of the patient and to allow activities of daily living. Embodiments hereof are directed to a low profile and light weight nasal interface that is configured to provide improved entrainment of ambient air so as to conserve the amount of compressed respiratory gas used by a patient while providing increased ventilatory support and/or positive airway pressure.